The present invention relates to xanthine derivatives having anti-dementia activity and being useful as an anti-dementia drug.
Xanthine derivatives have been hitherto known in the prior art. For example, U.S. Pat. No. 5,068,236 (Japanese Published Unexamined Patent Application No. 173888/92) discloses xanthine derivatives of the formula: ##STR4## wherein R.sup.A and R.sup.B are lower alkyl; and R.sup.C and R.sup.D are substituted or unsubstituted alicyclic alkyl. The xanthine derivatives have exhibited diuretic activity, renal protecting activity and vasodilator activity.
EP 415456A (Japanese Published Unexamined Patent Application No. 173889/92) discloses xanthine derivatives of the formula: ##STR5## wherein R.sup.E and R.sup.F is lower alkyl; and Q.sup.A represents ##STR6## (wherein is a single bond or double bond; Y.sup.A is a single bond or alkylene; and n.sup.a is 0 or 1).
Molecular Pharmacology, 33, 585 (1988) discloses a xanthine derivative of the formula: ##STR7## which has adenosine A.sub.1 antagonistic activity.
Journal of Medicinal Chemistry, 31, 745 (1988) discloses a xanthine derivative of the formula: ##STR8## which has adenosine A.sub.1 antagonistic activity.
European Journal of Medicinal Chemistry, 25, 653 (1990) discloses xanthine derivatives of the formula: ##STR9## wherein Q.sup.B is alkyl. The xanthine derivatives have bronchodilator activity.
CP 724173 discloses xanthine derivatives of the formula: ##STR10## R.sup.G and R.sup.H are alkyl or aralkyl; and Q.sup.C is cycloalkyl. The xanthine derivatives have diuretic activity.
Further, WO 86/01724 discloses an insecticide containing xanthine derivatives of the formula: ##STR11## wherein R.sup.J, R.sup.K and Q.sup.D and are substituted or unsubstituted aliphatic or alicyclic hydrocarbon having 1 to 8 carbon atoms (substituents are selected from halogen, alkyl and hydroxy) or substituted or unsubstituted aromatic hydrocarbon (substituents are selected from halogen, alkyl and hydroxy) or phenethyl.
EP 203721A (Japanese Published Unexamined Patent Application No. 42986/87) discloses xanthine derivatives of the formula: ##STR12## wherein R.sup.L and R.sup.M are alkyl or amino-substituted aralkyl; one of R.sup.N and R.sup.P is hydrogen and the other is --Y.sup.B --Z (wherein Y.sup.B is alkenylene and Z is carboxy). The xanthine derivatives have adenosine antagonistic activity.